support local import

[timotheecour]

support local import

eg use case:

when true:
  import std/strtabs
  block execProcessTest:
    var result = execCmdEx("nim r --hints:off -", options = {}, input = "echo 3*4")
    stripLineEnd(result[0])
    doAssert result == ("12", 0)
    doAssert execCmdEx("nonexistant").exitCode != 0
    when defined(posix):
      doAssert execCmdEx("echo $FO", env = newStringTable({"FO": "B"})) == ("B\n", 0)
      doAssert execCmdEx("echo $PWD", workingDir = "/") == ("/\n", 0)

links

• allow import inside block: makes N runnableExamples run N x faster, minimizes scope pollution · Issue #9300 · nim-lang/Nim
• comment nim dump is roughly 100x slower in 1.3 versus 1.2 nim-lang/Nim#14179 (comment)

That's a topic for another discussion, but allowing local imports (eg at proc scope) would solve many dependency issues, including the one that causes this regression, making importing more lazy. I even have a working branch for that.

EDIT: see https://github.com/nim-lang/Nim/pull/18734